This invention relates to a novel control valve assembly adaptable for use in controlling the movement of a fluid powered motor unit. In particular, the present invention is directed to a spool-type hydraulic control valve interrelated with a stem-type check valve assembly.
Fluid power motors have many uses, as for example, controlling the pivoting motion of a loaded forklift arm. A serious problem arises when it is desired to pivot an elevated load in a direction away from the motor unit in that the weight of the load tends to increase the pivoting speed of the arm faster than the drive chamber of the fluid motor can be filled with pressurized hydraulic fluid. The lack of sufficient hydraulic fluid creates a cavity in the loading chamber preventing the fluid powered motor from accurately controlling and stopping the pivoting motion of the elevated load, resulting in serious damage to the forklift mechanism.
In an attempt to solve the above-stated problem, the industry has turned to a variety of control devices, including both tilt lock mechanisms and check valve assemblies. None of the prior art devices known to the applicant have proved satisfactory in providing an economical, unitary device for positively controlling the movement of a fluid powered motor which prevents leakage in the hydraulic fluid circuitry and drift induced by the weight of the load.